Is this basically "How do I know which system files are needed" but expanded to include arbitrary third party software as well? It seems like it's too broad for a quick answer - but I'd rather get it honed down before closing it for that reason.
– bmike♦Jul 1 '13 at 18:20

Sounds good - ping me if you want this reopened. You'll want to be precise about what "Unused" means since OS X writes files once the first time you boot, but the files are still "used" each boot to know that a certain setup is complete. In practice, deleting files from Library is a really nice way to break things at a later date when a seldom used file is needed and missing.
– bmike♦Jul 1 '13 at 18:25

Unused means if it is not in my application folder nor it belongs to os x ! or when I delete it it should remove any residue from the Library., I decide to try the omnidisksweepr app.
– RuskesJul 1 '13 at 18:32

Let's give it a shot - try to take an edit to remove most of the answer from above and answer the question - perhaps that will reduce the chance of votes to close.
– bmike♦Jul 1 '13 at 20:47